Protein arginine N-methyltransferases (PRMTs) are physiologically important enzymes. In different proteins they methylate arginine residues in signaling pathways and gene expression. PRMTs are mechanistically complex and demonstrate variable dimethylation processivity (the ability to catalyze consecutive reactions without releasing the substrate). It is unclear whether these enzymes bind their target and cofactor substrates randomly or sequentially.

Nathaniel I. Martin, University of Utrecht, The Netherlands, Adam Frankel, University of British Columbia, Vancouver, Canada, and colleagues have performed kinetic studies using radiolabeled methyl groups to better understand PRMTs. The researchers demonstrated that the PRMT1 processivity depends on both cofactor and enzyme concentration, which indicates that the experimental design profoundly affects substrate dimethylation.

Furthermore, the team showed that PRMT1 binds its substrates using a so-called sequentially ordered Bi–Bi mechanism (a type of reaction involving two substrates and two products). Considering the structural and functional conservation among PRMTs, these insights could be applicable throughout the PRMT family.

• Kinetic Analysis of PRMT1 Reveals Multifactorial Processivity and a Sequential Ordered Mechanism,
  Jennifer I. Brown, Timo Koopmans, Jolinde van Strien, Nathaniel I. Martin, Adam Frankel,
  ChemBioChem 2017.
  https://doi.org/10.1002/cbic.201700521